update

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1522 42af7a65-404d-4744-a932-0658087f49c3

configs/skp16c26/README.txt

 configs/skp16c26/README.txt
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-BUILDING THE R8C/M16C/M32C GNU TOOLCHAIN
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+1. The buildroot package can be used to build an M16C toolchain.  The toolchain
+   buildroot can be downloaded from misc/buildroot in the NuttX CVS.  Insructions
+   for building the toolchain are provided below.
+
+   However, the target cannot be built because the GNU m16c-elf-ld link fails with 
+   the following message:
+
+     m32c-elf-ld: BFD (GNU Binutils) 2.19 assertion fail /home/Owner/projects/nuttx/buildroot/toolchain_build_m32c/binutils-2.19/bfd/elf32-m32c.c:482
+
+   Where the reference line is:
+
+     /* If the symbol is out of range for a 16-bit address,
+        we must have allocated a plt entry.  */
+     BFD_ASSERT (*plt_offset != (bfd_vma) -1);
+
+   No workaround is known at this time.  This is a show stopper for M16C.
+
+2. A supported version of the M16C toolchain is available here: 
+
+     http://www.kpitgnutools.com/index.php
+
+   This download is free but requires registration.  Unfortunately, this v0901 of
+   this toolchain shows the same behavior:
+
+   c:\Hew3\Tools\KPIT Cummins\GNUM16CM32C-ELF\v0901\m32c-elf\bin\m32c-elf-ld.exe: BFD (GNU Binutils) 2.19-GNUM16CM32C_v0901 assertion fail /home/kpit/fsfsrc/binutils-2.19/bfd/elf32-m32c.c:482
+
+It is possible that this error messasge my be telling me -- a very roundabout way --
+that I have exceeded the FLASH region, but I think that unlikely (it is difficult
+to know if the link does not complete gracefully).
+
+BUILDING THE R8C/M16C/M32C GNU TOOLCHAIN USING BUILDROOT
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+NOTE:  See the toolchain issues above -- you may not want to waste your time.
 
 1. CD to the correct directory.